Bottles of this type have been described under several concrete embodiments in various earlier patents of the same applicant company. In these bottles, a bifunctional membrane is placed at one end of the expulsion channel, upstream of the path for the expelled liquid, in order to allow an alternation between the passage of the expelled liquid and the passage of the entering air. The same membrane is used as an anti-bacterial membrane preventing the passage of impurities when air enters back into the bottle. It is a constant objective of the applicant to propose bottle assemblies allowing the absence of external contamination of the liquid contained in the reservoir. It is further a constant purpose of the applicant to ensure the delivery of drops conveniently shaped and calibrated, without any leakage, and that purpose find benefits from a good governing of the alternation between the fluid flows through a same channel, the liquid flow in one direction and the air flow in the opposite direction.
It is in this context that the invention aims at proposing a head for the delivery of drops that is more efficient in maintaining the sterility of the liquid and that is particularly simple and cheap to manufacture.